IP Timing Wayyy Off - Benzworld.org - Mercedes-Benz Discussion Forum

NOPEC · 02-20-2012, 10:18 AM

In preparation to sell my 1984 300d I did a valve adjustment. While everything was open, I decided to check my timing chain. It is maybe 1-2 degress off TDC, not bad. Then, for the hell of it, I decided to check my IP timing (well method).

WHOA!

It starts welling up around 47!!! Spin around again, stop at 40 as described in my manual... Welling up. OK, move to 24 btdc, soak up fuel... no welling. Is it possible to be this far off????

I search the forums and no one has mentioned being this far off!

TIA
-Tom

300Dman · 02-20-2012, 11:13 AM

Some claim that the non-Mercedes approved timing methods are not accurate.

Army · 02-20-2012, 12:43 PM

I would either re-do the test you've done or do another test - like the drip test - before adjusting the position of the IP. Before you adjust I'd make sure that you can repeat the test and get the same results several times in a row...

...this situation has tripped up many a DIY mechanic. You could end up chasing your tail.

NOPEC · 02-20-2012, 01:45 PM

I'll see if I can do the drip test. Seems easy enough.

Govert70227 · 02-20-2012, 02:26 PM

If it was really at 47º BTDC, your engine would run pretty badly. The diesel fuel would ignite before the piston reached the TDC, so the force of the combustion would work against the piston moving up. I don't think your car would run with IP timing at 47º.

The well-up method is described in the FSM for the fintail (Heckflosse) model, but you have to use a capillary tube screw on the delivery valve holder. The FSM adds that this method is less accurate than the drip method.

NOPEC · 02-21-2012, 01:55 PM

Today I performed the drip test.

Not so good. Nothing was happening at 24 degrees. I slowly hand cranked it a few times and did notice that fuel came out around 90 degrees (???) and then about 23-24 degrees AFTER TDC!!!!

Last year I did my front main seal. Could it be possible that I put on the Balancer 180 degrees? I am trying to imagine what that would change but I can't wrap my head around it.

Thoughts?

It is going to the shop Thursday I guess.

Govert70227 · 02-21-2012, 02:11 PM

Start at about 30 degrees before TDC and move the engine degree by degree, testing at every degree. Note the point when it stops flowing and starts dripping. No fuel at 24º is not necessarely bad.

Once the piston of the pump moves down, fuel will start flowing out again.

NOPEC · 02-21-2012, 03:05 PM

As I turn the engine, are the numbers that are going down to 0 -Before TDC (BTDC)?

As it goes past 0, are the numbers going up- After TDC (ATDC)?

Govert70227 · 02-21-2012, 03:19 PM

Make sure your first cylinder is in the compression stroke: both cams are pointing upwards, exhaust is past the oil pipe, intake valve is before the oil pipe:

TDC is marked with OT (that is a German abbreviation Oberste Totpunkt = TDC).

Red is Before TDC, Green is After TDC

NOPEC · 02-21-2012, 03:21 PM

Thanks.. Some more reading and I think I know what I was doing wrong. I'll set another go tomorrow maybe. Apparently 24 is the LAST point fuel comes out, not the first. (right?)